Healable and Rearrangeable Networks of Liquid Crystal Elastomers Enabled by Diselenide Bonds

Tough and Photo-Plastic Liquid Crystal Elastomer with a 2-Fold Dynamic Linker for Artificial Muscles

Liquid crystal elastomers (LCEs) have been optimized by combining cross-linkers and dynamic bonds to achieve a reversible actuation behavior comparable to living skeletal muscles. In this study, one unique type of segment with 2-fold dynamic properties was introduced into LCEs, which offered not only dynamic diselenide covalent bonds for thermo-/photoplasticity but also H-bond arrays for dynamic cross-linking and mechanical robustness. Besides self-healing, self-welding, and recyclability, the LCEs were reprogrammable with elevated temperature or intensive visible light irradiation. The resultant LCEs gave an actuation blocking stress of 1.96 MPa and an elastic modulus of 14.4 MPa at 80 °C. The actuation work capacity reached 135.2 kJ m-3. When incorporating the Joule electrode or photothermal materials, the LCEs could be programmed as the electricity-driven and photothermal artificial muscles and thereby promised the application both as a biomimetic artificial hand and as an energy collector from sunlight. Thus, the 2-fold dynamic LCEs offered the pathway of enabling the reversible actuation behavior comparable to living skeletal muscles and promising applications in sustainable actuators, artificial muscles, and soft robots.

Springtail-inspired Light-driven Soft Jumping Robots Based on Liquid Crystal Elastomers with Monolithic Three-leaf Panel Fold Structure

Jump is an important form of motion that enables animals to escape from predators, increase their range of activities, and better adapt to the environment. Inspired by springtails, we describe a light-driven soft jumping robot based on a double-folded liquid crystal elastomer (LCE) ribbon actuator with a monolithic three-leaf panel fold structure. This robot can achieve remarkable jumping height, jumping distance, and maximum take-off velocity, of up to 87 body length (BL), 65 BL, and 930 BL s^-1 , respectively, under near-infrared light irradiation. Further, it is possible to control the height, distance, and direction of jump by changing the size and crease angle of the double-folded LCE ribbon actuators. These robots can efficiently jump over obstacles and can jump continuously, even in complex environments. Our simple design strategy improves the performance of jumping actuators and we expect it to have a wide-ranging impact on the strength, continuity, and adaptability of future soft robots.

Over 200 °C Broad-Temperature Lasers Reconstructed from a Blue-Phase Polymer Scaffold

Blue-phase liquid crystal (BPLC) lasers have received extensive attention and have potential applications in sensors, displays, and anti-counterfeiting, owing to their unique 3D photonic bandgap. However, the working temperature range of such BPLC lasers is insufficient, and investigations are required to elucidate the underlying mechanism. Herein, a broad-temperature reconstructed laser is successfully achieved in dye-doped polymer-stabilized blue-phase liquid crystals (DD-PSBPLCs) with an unprecedented working temperature range of 25-230 °C based on a robust polymer scaffold, which combines the thermal stability and the tunability from the system. The broad-temperature lasing stems from the high thermal stability of the robust polymerized system used, which affords enough reflected and matched fluorescence signals. The temperature-tunable lasing behavior of the DD-PSBPLCs is associated with the phase transition of the unpolymerized content (≈60 wt%) in the system, which endows with a reconstructed characteristic of BP lasers including a U-shaped lasing threshold, a reversible lasing wavelength, and an obvious lasing enhancement at about 70 °C. This work not only provides a new idea for the design of broad-temperature BPLC lasers, but also sets out important insight in innovative microstructure changes for novel multifunctional organic optic devices.

A diselenobis-functionalized magnetic catalyst based on iron oxide/silica nanoparticles suggested for amidation reactions

In this study, a new heterogeneous magnetic catalytic system based on selenium-functionalized iron oxide nanoparticles is presented and suggested for facilitating amide/peptide bonds formation. The prepared nanocatalyst, entitled as “Fe₃O₄/SiO₂-DSBA” (DSBA stands for 2,2′-diselanediylbis benzamide), has been precisely characterized for identifying its physicochemical properties. As the most brilliant point, the catalytic performance of the designed system can be mentioned, where only a small amount of Fe₃O₄/SiO₂-DSBA (0.25 mol%) has resulted in 89% reaction yield, under a mild condition. Also, given high importance of green chemistry, convenient catalyst particles separation from the reaction medium through its paramagnetic property (ca. 30 emu·g⁻¹) should be noticed. This particular property provided a substantial opportunity to recover the catalyst particles and successfully reuse them for at least three successive times. Moreover, due to showing other excellences, such as economic benefits and nontoxicity, the presented catalytic system is recommended to be scaled up and exploited in the industrial applications.

Highly Durable and Tough Liquid Crystal Elastomers

Liquid crystal elastomers (LCEs) are soft materials that exhibit interesting anisotropic and actuation properties. The emerging applications of thermally actuatable LCEs demand sufficient mechanical durability under various thermomechanical cycles. Although LCEs are tough at room temperature, they become very brittle at high temperature (above their actuation temperature), which can cause unexpected failure. We demonstrate a strategy to improve the high temperature fracture and fatigue properties of LCEs by designing interpenetrating polymer networks using a second polyurethane network. By selecting the appropriate composition of the polyurethane networks, the high temperature fracture and fatigue properties of LCEs were significantly enhanced, while retaining their actuation properties. The strategy from this work will help fabricate LCE-based actuators that are tough and durable at high temperatures and under cyclic loading.

Mechanochromic, Shape-Programmable and Self-Healable Cholesteric Liquid Crystal Elastomers Enabled by Dynamic Covalent Boronic Ester Bonds

Endowing a cholesteric liquid crystal elastomer (CLCE) exhibiting helicoidal nanostructure with dynamically tailorable functionalities is of paramount significance for its emerging applications in diverse fields such as adaptive optics and soft robotics. Here, a mechanochromic, shape-programmable and self-healable CLCE is judiciously designed and synthesized through integrating dynamic covalent boronic ester bonds into the main-chain CLCE polymer network. The circularly polarized reflection of CLCEs can be reversibly and dynamically tuned across the entire visible spectrum by mechanical stretching. Thanks to the introduction of dynamic boronic ester bonds, the CLCEs were found to show robust reprogrammable and self-healing capabilities. The research disclosed herein can provide new insights into the development of 4D (color and 3D shape) programmable photonic actuators towards bioinspired camouflage, adaptive optical systems, and next-generation intelligent machines.

Thermo- and Mechanochromic Camouflage and Self-Healing in Biomimetic Soft Actuators Based on Liquid Crystal Elastomers

In nature, many mysterious creatures capable of deformation camouflage, color camouflage, and self-healing have inspired scientists to develop various biomimetic soft robots. However, the systematic integration of all the above functionalities into a single soft actuator system still remains a challenge. Here we chemically introduce a multi-stimuli-responsive tetraarylsuccinonitrile (TASN) chromophore into a liquid crystal elastomer (LCE) network through a facile thiol-ene photoaddition method. The obtained TASN-LCE soft actuators not only exhibit reversible shape-morphing and reversible color-changing behavior in response to heat and mechanical compression, but also show excellent self-healing, reprogramming and recycling characteristics. We hope that such a TASN-LCE actuator system endowed with dynamic distortion, thermo- and mechano-chromic camouflage, and self-healing functionalities would pave the way for further development of multifunctional biomimetic soft robotic devices.

One-Pot Synthesis of Melt-Processable Supramolecular Soft Actuators

The application of reprocessable and reprogrammable soft actuators is limited by the synthetic strategies, 3D‐shaping capabilities, and small deformations. In this work, melt‐processable supramolecular soft actuators based on segmented copolymers containing thiourethane and liquid crystal segments have been prepared via sequential thiol addition reactions in a one‐pot approach using commercially available building blocks. The actuators demonstrated immediate, reversible response and weightlifting capabilities with large deformations up to 32 %. Through exploiting the supramolecular cross‐links, the material could be recycled and reprogrammed into 3D actuators and welded into an actuator assembly with different deformation modes. Our work offers a one‐pot synthesis and straightforward melt‐processable approach to prepare supramolecular soft actuators with large deformations that can be reprocessed and reprogrammed into arbitrary 3D shapes.